This invention relates to improvements in a bidirectional flow filter-drier assembly for use in the liquid line of reverse-cycle refrigeration and air-conditioning systems, more commonly known as heat pumps.
There are many filter-driers in existence which have been and can be used in heat pumps, but these filter-driers are designed for refrigerant flow in one direction only so that if there is a backflow, solid contaminants that were picked up in the forward flow direction are released to the system. Consequently, the use of these existing filter-driers requires the use of additional bypass valves and piping that restrict flow in one direction.
Of course, an alternative to installing the existing filter-drier in the liquid line of a heat pump system, would be to install such filter-drier in the common suction line. However, such a filter-drier would have to be materially larger in size to minimize pressure drop because it would be handling vapor rather than liquid flow. In any event, many system designers prefer the filter-drier to be located in the liquid line to protect the expansion valves. These existing filter-driers cannot be back-flowed without detrimental effects, and their use in the liquid line requires additional bypass valves, and their use in the suction line requires an oversized unit and leaves the expansion devices directly unprotected from contamination.